Multiple clutch module

ABSTRACT

A multiple clutch module for an automatic transmission integrates at least two multi-plate wet clutches into a single module. Each of the clutches includes a set of separator plates interleaved with at least one friction plate and a piston configured to compress the separators plates and friction plates. The separator plates of the first clutch are splined to a housing along their inner diameter whereas the separator plates of the second clutch are splined to the housing along their outer diameter. Each piston is associated with an apply chamber and a balance chamber radially inside the respective separator plates and friction plates. The housing rotates about a central shaft. Pressurized fluid is supplied to the clutches from the shaft. The first and second balance chambers are connected by a passageway within the housing such that they can be supplied with fluid from a common orifice in the housing.

TECHNICAL FIELD

This disclosure relates to the field of automatic transmissions formotor vehicles. More particularly, the disclosure pertains to aconfiguration of clutches for use in a transmission.

BACKGROUND

Many vehicles are used over a wide range of vehicle speeds, includingboth forward and reverse movement. Some types of engines, however, arecapable of operating efficiently only within a narrow range of speeds.Consequently, transmissions capable of efficiently transmitting power ata variety of speed ratios are frequently employed. When the vehicle isat low speed, the transmission is usually operated at a high speed ratiosuch that it multiplies the engine torque for improved acceleration. Athigh vehicle speed, operating the transmission at a low speed ratiopermits an engine speed associated with quiet, fuel efficient cruising.Typically, a transmission has a housing mounted to the vehiclestructure, an input shaft driven by an engine crankshaft, and an outputshaft driving the vehicle wheels, often via a differential assemblywhich permits the left and right wheel to rotate at slightly differentspeeds as the vehicle turns.

A common type of automatic transmission utilizes a collection ofclutches and brakes. Various subsets of the clutches and brakes areengaged to establish the various speed ratios. A common type of clutchutilizes a clutch pack having separator plates splined to a housing andinterleaved with friction plates splined to a rotating shell. When theseparator plates and the friction plates are forced together, torque maybe transmitted between the housing and the shell. Typically, a separatorplate on one end of the clutch pack, called a reaction plate, is axiallyheld to the housing. A piston applies axial force to a separator plateon the opposite end of the clutch pack, called a pressure plate,compressing the clutch pack. The piston force is generated by supplyingpressurized fluid to a chamber between the housing and the piston. For abrake, the housing may be integrated into the transmission case. For aclutch, the housing rotates. As the pressurized fluid flows from thestationary transmission case to the rotating housing, it may need tocross one or more interfaces between components rotating at differentspeeds. At each interface, seals direct the flow from an opening in onecomponent into an opening in the interfacing component.

SUMMARY OF THE DISCLOSURE

A transmission includes a clutch housing, three clutch packs, and threepistons. The first and second of the three clutch packs includeseparator plates splined to the housing and friction plates splined tofirst and second shells, respectively. An input shaft extends throughthe housing. The third of the three clutch packs includes separatorplates splined to the input shaft and friction plates splined to thesecond shell. The three pistons are configured to apply force to therespective clutch packs. A sun gear of a first planetary gear set may befixedly coupled to the second shell. The transmission may also include asecond planetary gear set with a sun gear fixedly coupled to the firstshell and a ring gear fixedly coupled to the housing.

In one embodiment, a clutch module includes a housing configured torotate about a shaft, a first set of separator plates splined to thehousing along their outer edges, and a second set of separator platessplined to the housing along their inner edges. The inner diameter ofthe second separator plates is less than the outer diameter of the firstseparator plates. The clutch module may also include a first pistonconfigured to apply force to the first separator plates and, inconjunction with the housing, defining a first apply chamber with anouter diameter less than the inner diameter of the first separatorplates. The clutch module may also include a second piston configured toapply force to the second separator plates and, in conjunction with thehousing, defining a second apply chamber with an outer diameter lessthan the inner diameter of the second separator plates. The housing,first piston, and second piston, may also define first and secondbalance chambers connected to one another by a passageway.

In another embodiment, a clutch module includes a housing configured torotate about a shaft, two clutch packs, and two pistons. The clutchpacks each includes separator plates splined to the housing andinterleaved with friction plates. The first and second pistons areconfigured to compress the first and second clutch packs, respectively.The pistons and the housing define first and second apply chambers. Theouter diameter of the first apply chamber is less than the innerdiameter of the first separator plates. Similarly, the outer diameter ofthe second apply chamber is less than the inner diameter of the secondseparator plates. The housing may be fixedly coupled to a ring gear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a transmission gearing arrangement.

FIG. 2 is a cross section of one of the clutches and one of theplanetary gear sets of a transmission according to the gearingarrangement of FIG. 1.

FIG. 3 is a cross section of three of the clutches and one of theplanetary gear sets of a transmission according to the gearingarrangement of FIG. 1.

FIG. 4 is a cross section of three of the clutches and one of theplanetary gear sets of a transmission according to the gearingarrangement of FIG. 1.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

A gearing arrangement is a collection of rotating elements and shiftelements configured to impose specified speed relationships among therotating elements. Some speed relationships, called fixed speedrelationships, are imposed regardless of the state of any shiftelements. Other speed relationships, called selective speedrelationships, are imposed only when particular shift elements are fullyengaged. A discrete ratio transmission has a gearing arrangement thatselectively imposes a variety of speed ratios between an input shaft andan output shaft.

A group of rotating elements are fixedly coupled to one another if theyare constrained to rotate as a unit in all operating conditions.Rotating elements can be fixedly coupled by spline connections, welding,press fitting, machining from a common solid, or other means. Slightvariations in rotational displacement between fixedly coupled elementscan occur such as displacement due to lash or shaft compliance. Incontrast, two rotating elements are selectively coupled by a shiftelement when the shift element constrains them to rotate as a unitwhenever it is fully engaged and they are free to rotate at distinctspeeds in at least some other operating condition. A shift element thatholds a rotating element against rotation by selectively connecting itto the housing is called a brake. A shift element that selectivelycouples two or more rotating elements to one another is called a clutch.Shift elements may be actively controlled devices such as hydraulicallyor electrically actuated clutches or brakes or may be passive devicessuch as one way clutches or brakes.

An example transmission is schematically illustrated in FIG. 1. Thetransmission utilizes four simple planetary gear sets 20, 30, 40, and50. A planet carrier 22 rotates about a central axis and supports a setof planet gears 24 such that the planet gears rotate with respect to theplanet carrier. External gear teeth on the planet gears mesh withexternal gear teeth on a sun gear 26 and with internal gear teeth on aring gear 28. The sun gear and ring gear are supported to rotate aboutthe same axis as the carrier. Gear sets 30, 40, and 50 are similarlystructured.

A suggested ratio of gear teeth for each planetary gear set is listed inTable 1.

TABLE 1 Ring 28/Sun 26 2.20 Ring 38/Sun 36 1.75 Ring 48/Sun 46 1.60 Ring58/Sun 56 3.70

In the transmission of FIG. 1, sun gear 26 is fixedly coupled to sungear 36, carrier 22 is fixedly coupled to ring gear 58, ring gear 38 isfixedly coupled to sun gear 46, input shaft 60 is fixedly coupled tocarrier 32, and output shaft 62 is fixedly coupled to carrier 52. Ringgear 28 is selectively held against rotation by brake 66 and sun gears26 and 36 are selectively held against rotation by brake 68. Input shaft60 is selectively coupled to sun gear 56 by clutch 70. Ring gear 48 isselectively coupled to sun gear 56 by clutch 72 and selectively coupledto ring gear 38 and sun gear 46 by clutch 76. Carrier 42 is selectivelycoupled to carrier 22 and ring gear 58 by clutch 74.

As shown in Table 2, engaging the shift elements in combinations of fourestablishes ten forward speed ratios and one reverse speed ratio betweeninput shaft 60 and output shaft 62. An X indicates that the shiftelement is required to establish the speed ratio. An (X) indicates theshift element can be applied but is not required. In 1^(st) gear, eitherclutch 74 or clutch 76 can be applied instead of applying clutch 72without changing the speed ratio. When the gear sets have tooth numbersas indicated in Table 1, the speed ratios have the values indicated inTable 2.

TABLE 2 66 68 70 72 74 76 Ratio Step Rev X X X X −4.79 102% 1^(st) X X X(X) 4.70 2^(nd) X X X X 2.99 1.57 3^(rd) X X X X 2.18 1.37 4^(th) X X XX 1.80 1.21 5^(th) X X X X 1.54 1.17 6^(th) X X X X 1.29 1.19 7^(th) X XX X 1.00 1.29 8^(th) X X X X 0.85 1.17 9^(th) X X X X 0.69 1.24 10^(th)X X X X 0.64 1.08

FIG. 2 shows a cross sectional view of the center section of atransmission according to the gearing arrangement of FIG. 1. The crosssection of FIG. 2 is taken between the planetary gears 44 of gear set40. Housing 80 of clutch 74 is integrated with the carrier 42 of gearset 40. A collection of separator plates 82 is splined at their inneredges to housing 80. A collection of friction plates 84 is interleavedwith separator plates 82 and splined at their outer edges to shell 86.Shell 86 is fixedly coupled to carrier 22 and ring gear 58. Piston 88 issupported to slide axially within housing 80. The contact points betweenhousing 80 and piston 88 have seals such that housing 80 and piston 88define two chambers 90 and 92. The chambers have inner and outerdiameters defined by the contact points between the housing and thepiston. Clutch 74 is engaged by pressurizing fluid in clutch applychamber 90 such that piston 88 slides toward gear set 40 and compressesfriction plates 84 between separator plates 82. When housing 80 rotates,centrifugal forces may pressurize fluid within clutch apply chamber 90which could potentially result in unintended engagement of clutch 74.However, fluid in balance chamber 92 is subject to the same centrifugalforces, exerting a compensating force on piston 88 to preclude thisfailure mode. Fluid reaches chambers 90 and 92 via axial passageways ininput shaft 60 then through holes in hollow shaft 94. Hollow shaft 94 isfixedly coupled to ring gear 38 and sun gear 46. Return spring 96, whichextends into the space between planet gears, forces piston 88 to slideaway from gear set 40 when pressure in chamber 90 is relieved.

FIG. 3 shows a cross sectional view of a transmission according to thegearing arrangement of FIG. 1 slightly rearward from the view of FIG. 2.The cross section of FIG. 3 is taken through the center of one of theplanetary gears 44 of gear set 40. Housing 98 of clutches 72 and 74 isfixedly coupled to ring gear 48 of gear set 40. A collection ofseparator plates 100 is splined at their outer edges to housing 98. Acollection of friction plates 102 is interleaved with separator plates100 and splined at their inner edges to shell 104. Shell 104 is fixedlycoupled to hollow shaft 94. Piston 106 is supported to slide axiallywithin housing 98. Housing 98 and piston 106 define two chambers 108 and110. Clutch 76 is engaged by pressurizing fluid in clutch apply chamber108 such that piston 106 slides toward gear set 40 and compressesfriction plates 102 between separator plates 100. Centrifugal forceacting on the fluid in balance chamber 110 compensates for centrifugalforce acting on the fluid in clutch apply chamber 108. Return spring 112forces piston 106 to slide away from gear set 40 when pressure inchamber 108 is relieved.

A collection of separator plates 114 is splined at their inner edges tohousing 98. A collection of friction plates 116 is interleaved withseparator plates 114 and splined at their outer edges to shell 118.Shell 118 is fixedly coupled to sun gear 56. Piston 120 is supported toslide axially within housing 98. Housing 98 and piston 120 define twochambers 122 and 124. Clutch 72 is engaged by pressurizing fluid inclutch apply chamber 122 such that piston 120 slides toward gear set 40and compresses friction plates 116 between separator plates 114.Centrifugal force acting on the fluid in balance chamber 124 compensatesfor centrifugal force acting on the fluid in clutch apply chamber 120.Return spring 126 forces piston 120 to slide away from gear set 40 whenpressure in chamber 122 is relieved. Fluid reaches chambers 108, 110,122, and 124 via axial passageways in input shaft 60. A passagewaywithin housing 98 connects balance chambers 110 and 124.

Housings 80 and 98 are described as single components. However, theylikely would be manufactured in several pieces which are fastenedtogether during assembly. Clutch 74 may be assembled before installationinto the transmission. Similarly, clutches 76 and 72 may be assembledinto a two clutch module before installation into the transmission.

FIG. 4 shows a cross sectional view of a transmission according to thegearing arrangement of FIG. 1 slightly rearward from the view of FIG. 3.Housing 128 of clutch 70 is fixedly coupled to input shaft 60. Acollection of separator plates 130 is splined at their inner edges tohousing 128. A collection of friction plates 132 is interleaved withseparator plates 130 and splined at their outer edges to shell 118.Piston 134 is supported to slide axially within housing 128. Housing128, piston 134, and input shaft 60 define two chambers 136 and 138.Clutch 70 is engaged by pressurizing fluid in clutch apply chamber 136such that piston 134 slides toward gear set 40 and compresses frictionplates 132 between separator plates 130. Centrifugal force acting on thefluid in balance chamber 138 compensates for centrifugal force acting onthe fluid in clutch apply chamber 136. Return spring 140 forces piston134 to slide away from gear set 40 when pressure in chamber 136 isrelieved.

A single passageway in input shaft 60 supplies unpressurized fluid tobalance chambers 92, 110, 124, and 138. The same passageway may supplyfluid to other parts of the transmission for lubrication. Separatepassageways supply clutch apply chambers 90, 108, 122, and 136 such thateach clutch may be engaged and disengaged independently of the otherclutches. Fluid may flow into these five passageways in input shaft 60either from a front support, through the output shaft, or a combinationof these.

The configuration of clutches in FIGS. 2-4 places the apply chamber andbalance chamber at the same axial position and radially inside therespective clutch pack. This reduces the axial length of thetransmission relative to placing the clutch packs axially in line withthe apply chamber and balance chamber. Since fluid pressure is suppliedto the clutches from central shaft, locating the chambers near thecenterline reduces the need for radial passageways. Furthermore, sincethe torque capacity of each clutch is directly proportional to the meandiameter of the clutch pack, locating the clutch packs radially outsideof the apply chambers reduces the number of friction plates required orthe required area of the apply chamber.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes can be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments can becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics can becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes caninclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and can be desirable for particularapplications.

1. A transmission comprising: a clutch housing; a first clutch packhaving first separator plates splined to the clutch housing and a firstfriction plate splined to a first shell; a first piston configured toslide axially within the clutch housing and apply force to the firstclutch pack; a second clutch pack having second separator plates splinedto the clutch housing and a second friction plate splined to a secondshell; a second piston configured to slide axially within the clutchhousing and apply force to the second clutch pack; an input shaftextending through the housing; a third clutch pack having thirdseparator plates splined to the input shaft and a third friction platesplined to the second shell; and a third piston configured to applyforce to the third clutch pack.
 2. The transmission of claim 1 furthercomprising a first planetary gear set having a first sun gear fixedlycoupled to the second shell, a first carrier, a first ring gear, and aplurality of planet gears supported on the first carrier and meshingwith the first sun gear and the first ring gear.
 3. The transmission ofclaim 2 further comprising a second planetary gear set having a secondsun gear fixedly coupled to the first shell, a second carrier, a secondring gear fixedly coupled to the housing, and a plurality of planetgears supported on the second carrier and meshing with the second sungear and the second ring gear.
 4. A clutch module comprising: a housingconfigured to rotate about a shaft; a plurality of first separatorplates having outer edges splined to the housing, the first separatorplates having inner and outer diameters; and a plurality of secondseparator plates having inner edges splined to the housing, the secondseparator plates having an inner diameter less than the outer diameterof the first separator plates.
 5. The clutch module of claim 4 furthercomprising a first piston interfacing with the housing to define a firstapply chamber having an outer diameter less than the inner diameter ofthe first separator plates.
 6. The clutch module of claim 4 furthercomprising a second piston interfacing with the housing to define asecond apply chamber having an outer diameter less than the innerdiameter of the second separator plates.
 7. The clutch module of claim 4further comprising: a first piston interfacing with the housing todefine a first apply chamber and a first balance chamber; and a secondpiston interfacing with the housing to define a second apply chamber anda second balance chamber; wherein the housing defines a passagewayconnecting the first balance chamber to the second balance chamber. 8.The clutch module of claim 4 further comprising: a first plurality offriction plates interspersed with the first plurality of separatorplates and splined to a first shell, the first shell fixedly coupled toa first rotating element; and a second plurality of friction platesinterspersed with the second plurality of separator plates and splinedto a second shell, the second shell fixedly coupled to a second rotatingelement; wherein the housing is axially located between the firstrotating element and the second rotating element.
 9. A clutch modulecomprising: a housing configured to rotate about a shaft; a first clutchpack having a plurality of first separator plates splined to the housingand interleaved with at least one first friction plate, the firstseparator plates having an inner diameter; a first piston configured tocompress the first clutch pack, the first piston interfacing with thehousing to define a first apply chamber, the first apply chamber havingan outer diameter less than the inner diameter of the first separatorplates; a second clutch pack having a plurality of second separatorplates splined to the housing and interleaved with at least one secondfriction plate, the second separator plates having an inner diameter;and a second piston configured to compress the first second clutch pack,the second piston interfacing with the housing to define a second applychamber, the second apply chamber having an outer diameter less than theinner diameter of the second separator plates.
 10. The clutch module ofclaim 9 further comprising a ring gear fixedly coupled to the housing.